I have installed the Lua Development Tools, both as a stand-alone IDE and as a plug-in for my main Eclipse application, but am unable to get it to display any Outline information for the .lua files in my project.

This is doubly odd as the project is a mix of Lua and XML, and the XML files are outlined properly despite there being no XML editor on offer.

I am quite willing to believe that the problem is my own stupidity, but I have been scrathcing my head over this on and off for days now and can't progress.

Care sharing an example of the files you're trying to edit?
You say they are a mix of XML and Lua... do they have a .xml file extension? If so, they are most likely opened by default by the XML editor in Eclipse, not the Lua one...

They're pretty standard Lua and XML. I didn't mean to imply that the syntaxes were mixed within a file - there are some XML files named *.xml and some Lua files named *.lua. The syntax colouring is working fine, I just have a blank outline

More information: the stand-alone installation doesn't syntax colour the XML and displays An outline is not available in the outline frame, which is greyed.

However the Lua files are syntax coloured and the outline frame it white with no message, presumably meaning that it can show an outline but there's nothing to show. Also, when I try to use 'Open Declaration' on an identifier it pings mw and does nothing. I'm making sure to use global variables to test this.

It's possible I have added the files to the project wrongly as I've been using Eclipse for only a couple weeks. I used File/Import/General/File System. But I can't a better way to do it and the documentation seems to say I've done the right thing